Circuit breakers for low voltages are generally known. A double contact lever, for example, which is provided at its free ends with contact pieces which each form the moving contact, is used to open and close the circuit breaker. The contact pieces of the moving contacts lie opposite a contact piece of a fixed contact in each case. The contact lever is rotatably mounted in a switching shaft and extends perpendicular to the longitudinal axis thereof, wherein its ends protrude from the switching shaft. The contact piece of the moving contact is mounted on one side of the external contour while a depression is provided on the opposite side in which a bolt extending parallel to the switching shaft is engaged.
The elastic forces of a pair of springs, the torsional moment of which pulls the contact lever in the closing direction and holds the double contact lever in its closed position, act on both ends of the bolt. The current through the circuit breaker flows via the contact lever and the two current feeds which are designed in the form of conductor loops. When a short circuit occurs, large electromagnetic forces are produced in the conductor loops and move the double contact lever into its open position. At the same time, it is necessary that the contact pieces separate relatively quickly in order to interrupt the current flow as quickly as possible but without the contact lever falling back into its closed position after opening.
Preventing the contact lever falling back by pulling the bolt into a latching notch has already been disclosed in DE 693 04 374 T2 (FR 2 688 626), the entire contents of which are hereby incorporated herein by reference. In doing so, the energy required to latch the bolt is taken from the kinetic energy of the contact lever, which in turn slows down the switch opening. The latching notch is part of a control contour (control cam), which because of its radial elevation in the region of the latching notch inhibits the movement of the bolt and therefore that of the contact lever in the closing direction, as it is associated with a corresponding counter moment which must first be overcome by the bolt. This prevents an unwanted falling back (reclosing) of the circuit breaker.